The recent ambush was emblematic of what some officers say has become a near-perpetual and increasingly violent conflict between police and gangs in tough, largely immigrant French neighborhoods that were the scene of a three-week paroxysm of rioting last year.

One small police union claims officers are facing a “permanent intifada.” Police injuries have risen in the year since the wave of violence.

National police reported 2,458 cases of violence against officers in the first six months of the year, on pace to top the 4,246 cases recorded for all of 2005 and the 3,842 in 2004. Firefighters and rescue workers have also been targeted – and some now receive police escorts in such areas.

On Sunday, a band of about 30 youths, some wearing masks, forced passengers out of a bus in a southern Paris suburb in broad daylight Sunday, set it on fire, then stoned firefighters who came to the rescue, police said. No one was injured. Two people were arrested, one of them a 13-year-old, according to LCI television.